Summary: LaunchDay adds product submission and user login

Why It Matters: The site is moving from a static event page to a platform where users can create accounts and submit their own products for future events.

What Changed:

• Added a "Sign in" button for user accounts.
• Added a "Submit my product" call to action.
• Displayed final engagement stats for 11 products, including "applaud" counts and deal unlocks.
• Added a public chat log showing real-time user interactions and feedback.
• Included a "Next LaunchDay" section with a TBD status.